Spring-less valve train for internal combustion engine

ABSTRACT

A rocker arm ( 210 ) for use in a reciprocating, internal combustion engine includes a tip ( 235 ) and a seat ( 240 ). The tip and seat are urged to move by cams ( 220, 225 ) on a shaft ( 230 ). As the shaft rotates, the cams alternately apply force to the tip and the seat, causing the rocker arm to rotate about a pivot shaft ( 215 ). A valve ( 100 ) and valve stem ( 110 ′) are attached to the rocker arm. The valve is urged to open and close by motion of the rocker arm. Thus the valve is opened and closed through the use of positive camming and reciprocating forces only. No conventional valve spring is required to close the valve. Thus valve floating at high engine speeds is prevented and engine performance is improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

My U.S. Pat. No. 7,228,829, granted 2007 Jun. 12, shows a valve timingadjustment system.

BACKGROUND

1. Field

The field is internal combustion engines and in particular valve trainstherefor.

2. Prior Art

Internal combustion engines generally comprise an engine block with oneor more cylinders. Each cylinder contains a reciprocating piston and atleast two openings that are opened and closed by valves. An inlet valveadmits a fuel-air mixture and an outlet valve permits exhaust gases toescape. Both valves are held normally closed by strong springs toprevent the unwanted escape of gases during the compression and powerstrokes of the engine. During operation of the engine, each valve isrepeatedly pushed open at predetermined times and rates by lobes on acamshaft that cam, either directly or indirectly, the ends of the valvestems, in well-known fashion. In many cases, the camshaft lobes cam onone end of a rocker arm that pivots about a central axis; the other endof the rocker arm opens the valve. In either arrangement, the camshaftworks against the force of the springs to open the valves periodically;the valves are closed by the springs when they are not cammed open.

FIG. 1 shows a side view of a prior-art valve 100 that seats within acylinder 101 in an engine block 105. Valve 100 has a stem 110 thatextends upward from block 105. The upper end of stem 110 is secured to abushing 115 that holds a spring 120 in compression against the top ofblock 105, thereby holding valve 100 in a normally-closed (up) positionas shown. A rocker arm 125 pivots on a shaft 130. A cam 135 having alobe 140 rotates on a camshaft 145 that is connected to the crankshaftby a timing belt or chain (not shown) so that the camshaft rotates insynchronism with the engine's crankshaft (not shown). When lobe 140rotates from the side position shown to an upward position (not shown)it pushes upward against the left side of rocker arm 125, causing arm125 to rotate in a clockwise (CW) direction about shaft 130. Arm 125pushes downward on valve stem 110, thereby opening valve 100, asindicated by dashed lines. When valve 100 is open gases can pass to orfrom cylinder 101 via an inlet or exhaust port 150. Each cylinder has aminimum of two such valves, an inlet and an outlet. The diameter ofvalve 100 is typically between 1.5 and 10 cm, depending upon the size ofthe engine. In an engine with a valve diameter of three cm, the travelof valve 100 between its open and closed conditions is about one cm.

Pushing the inlet and exhaust valves open against the opposing force ofthe springs uses energy that is derived from the combustion cycle of theengine. Friction at all points between the cam lobes and the valve stemscontributes to wear and heating of the engine and adds strain to theengine's timing belt, motor oil, and starter. This energy is lost andnot available at the engine's crankshaft. Also it creates additionalheat in the engine. This results in a reduction in engine efficiencythat is measurable in terms of shorter engine life and increased fuelconsumption. In addition, when the engine is operated at very highspeeds, the springs lack adequate force to close the valves before theyare to be opened again. When this happens, the rocker arm separates fromcontact with the valve stem and the valves are said to float, i.e.remain open. In this condition, engine output and efficiency drop tonearly zero.

SUMMARY

In accordance with an aspect of one embodiment, an internal combustionengine uses no strong springs to hold the inlet and exhaust valvesclosed. Instead, the valves are opened and closed at predetermined timesand rates by a camshaft that applies both opening and closing forces tothe inlet and exhaust valve stems. Removing the requirement to compressthe valve springs during engine operation results in improved engineefficiency that is realized in reduced fuel consumption, a lighterengine, lower engine wear, less heat, and improved engine performance.Since the valves are forced open and closed by the camshaft, floating ofthe valves at high speeds is prevented.

DRAWING FIGURES

FIG. 1 shows a prior-art valve system.

FIGS. 2 through 6 show aspects of a first embodiment.

FIG. 7 shows an alternative embodiment.

REFERENCE NUMERALS

100 Valve 101 Cylinder 105 Block 110 Stem 111 Shoulder 115 Bushing 120Spring 125 Arm 130 Pivot 135 Cam 140 Lobe 145 Shaft 150 Port 200 Hole205 Pin or rod 206 Spring 210 Arm 214 Fastener 215 Shaft 220 Cam 221Lobe 225 Cam 226 Lobe 230 Shaft 235 Tip 240 Seat 500 Shaft 505 Shaft

FIRST EMBODIMENT Description—FIGS. 2 through 4

FIG. 2 is a perspective view of a cam, rocker arm, and valve assembly.In one aspect of a first embodiment, a valve 100 seats in a cylinder 101(FIGS. 3 through 6) of an internal combustion engine (not shown). Avalve stem 110′ extends upward from valve 100. The diameter of the upperend of stem 110′ is reduced and passes through a hole 200 in a pin orrod 205 that is rotatably secured within a rocker arm 210. Stem 110′ hasa shoulder 111 in where the diameter of the upper portion of stem 110′decreases. This prevents the lower portion of stem 110′ from passinginto hole 200. The upper end of stem 110′ extends above pin 205. The topof pin 205 and a fastener 214 hold a spring 206 in compression. Fastener214 preferably is a bolt head that is secured to the top of stem 110′but can also be a bushing, clevis, etc. Fastener 214 can be adjustable,as in the case of a screw or bolt that screws into the upper end of stem110′, or non-adjustable as in the case of a clip. Thus valve 100 and itsstem 110′ are springably held captive in pin 205. Spring 206 is pushedupwardly when rod 205 is moved upwardly by the rocker arm and in turnpushes fastener 214 and hence valve 100 upwardly to a closed position.Spring 206 also accommodates tolerance variations and holds valve 100 ina closed position as the engine wears or changes dimensions due toheating and cooling. Thus spring 206 and shoulder 111 form a pair offacing shoulders that are pushed up and down, respectively, by rod 205.The strength and compression of spring 206 is significantly less thanthat of spring 120 (FIG. 1). As such, the energy spent in furthercompressing spring 206 during operation of the engine is negligible.

Two cams 220 and 225 having lobes 221 and 226, respectively, extendradially from a camshaft 230 that turns in synchronism with the engine'scrankshaft (not shown). Camshaft 230 is turned by a timing belt or chain(not shown) in conventional fashion. The shapes of cams 220 and 225 arecomplimentary, i.e., they work in concert to control the opening andclosing of valve 100. Cam 220 varies in thickness from a low point to along lobe 221 of uniform thickness. Cam 225 varies in thickness from auniform low region to a relatively short lobe 226. In this example, cams220 and 225 are shown in positions that cause valve 100 to be open. Aslobe 226 of cam 225 forces seat 240 downward, cam 225 causes valve 100to open and thus is an opening cam. When lobe 221 of cam 220 forces tip235 to the left, in turn causing arm 210 to rotate CCW, cam 220 causesvalve 100 to close and thus is a closing cam. Closing cam 220 has arelatively long lobe 221 that extends circumferentially approximately180 degrees around cam 220, thereby holding valve 100 closed during thecompression and combustion portions of the engine cycle. Opening cam 225has a relatively short lobe 226 that extends circumferentially about 90degrees around cam 225 resulting in a shorter open time for valve 100,suitable for the relatively shorter-duration intake and exhaust portionsof the engine cycle. The difference in height between the low point andthe high points of cams 220 and 225 is preferably about one cm, althoughother heights can be used. Other cam profiles are possible and providefor different opening and closing rates and travel of valve 100, as willbe apparent to those skilled in the art.

Rocker arm 210 pivots about its central point on a shaft 215. Rocker arm210 includes two cam follower surfaces: a tip 235 and a seat 240. Tip235 is positioned to contact and follow cam 220. Seat 240 is positionedto contact and follow cam 225. All parts are made of steel, althoughother materials can be used. Tip 235, cams 220 and 225, and seat 240 aremade of hardened steel.

Operation—FIGS. 3 and 4

FIGS. 3 through 6 show cross-sectional views of rocker arm 210 atvarious positions of cams 220 and 225, respectively. FIGS. 3 and 4 showthe position of the various components at the instant when valve 100 isfully open. FIGS. 5 and 6 show the position of the components when valve100 is fully closed. FIGS. 3 through 6 each show a valve in order toindicate operation of the valve assembly. However, only one valve ispresent for each pair of cams 220 and 225.

FIGS. 3 and 4 show the valve opened: lobe 221 (FIG. 3) of closing cam220 is at its lowest point relative to shaft 230 and tip 235 of therocker arm bears against the non-lobed portion of closing cam 220. Atthe same point in time, the highest point of lobe 226 (FIG. 4) cams seat240, urging arm 210 to rotate CW about shaft 215 and forcing rod 205 toits lowest position, thereby moving shoulder 111 and hence valve 100down to the valve's most open position.

FIGS. 5 and 6 show the valve closed: as shaft 230 rotates CW, lobe 221of closing cam 220 rotates from its lowest point (FIG. 3) to its highestpoint (FIG. 5) where it cams tip 235 of arm 210, thereby causing arm 210to rotate counter-clockwise (CCW) on shaft 215 and urging rod 205 in anupward direction, thereby forcing spring 206 and hence fastener 214 andvalve 100 upwardly so that valve 100 seats in its closed position inblock 105. At the same time, lobe 226 of cam 225 (FIG. 6) has rotated sothat its lowest point relative to shaft 230 bears against seat 240,thereby permitting valve 100 to close.

Thus as shaft 230 turns CW, opening cam 225 and seat 240 urge rocker arm210 to rotate CW about shaft 215, forcing valve 100 to open, and thenclosing cam 220 and tip 235 urge rocker arm to rotate CCW about shaft215, forcing valve 100 to close, and so on. Thus the timing of theopening and closing of valve 100 is determined entirely by the shapes ofclosing and opening cams 220 and 225. The maximum height of closing cam220 is chosen to cause arm 210 to rotate CCW sufficiently to compressspring 206 slightly, thereby assuring that valve 100 will fully closedespite manufacturing tolerances and dimensional changes in the engine(not shown) as it heats and cools.

Closing cam 220 and tip 235 of rocker arm 210 ensure that valve 100 willfully close with each compression and combustion cycle of the engine.This prevents valve floating at high engine speeds.

FIRST ALTERNATIVE EMBODIMENT Description and Operation FIG. 7

FIG. 7 shows one aspect of an alternative embodiment. Instead of beingdisplaced side-by-side on rocker arm 210 (FIG. 2), tip 235 and seat 240lie in the same vertical plane. Instead of rotating on a single camshaft230 (FIG. 2), closing and opening cams 220 and 225 rotate on separateshafts 500 and 505, respectively. A timing belt or chain (not shown),well-known in the art, causes shafts 500 and 505 to rotate insynchronism with the engine's crankshaft (not shown).

As shaft 505 rotates, lobe 226 of opening cam 225 cams seat 240, forcingarm 210′ to rotate CW about shaft 215, thereby opening valve 100. Asshaft 500 continues to rotate, lobe 221 of closing cam 220 cams tip 235of arm 210′ to the left, causing arm 210′ to rotate CCW, thereby closingvalve 100, and so on.

As in the previous embodiment, the present arrangement ensures thatvalve 100 is opened and closed at the proper times, without the use ofthe prior-art spring.

SUMMARY, RAMIFICATIONS, AND SCOPE

The embodiments shown of my improved valve driving arrangements forinternal combustion engines result in an engine having improvedperformance, less internal wear, fewer parts, less heat, and lower cost.Without the large and forceful (stiff) prior-art valve springs, manycomponents, such as the cylinder head, starter motor, rocker arm, andcam lobe can be made smaller and lighter. Those skilled in the art canshape the contours of the cam lobes for optimum performance of eachengine.

While the above description contains many specificities, these shouldnot be considered limiting but merely exemplary. Many variations andramifications are possible. For example, instead of a finger on therocker arm, a roller bearing can be used. Instead of a coil spring tocompensate for dimensional changes, a leaf spring or Belleville springwasher can be used. Instead of the stem of the valve having a narrowedportion and extending through the rod, the stem can have a uniformdiameter with two projecting spaced shoulders or collars that can bepushed up and down (either directly or via one or two springs similar tospring 206) by the rod. Also the rod can extend through a hole in thestem. While the description of the embodiments discusses one valve inone cylinder for ease and simplification of explanation, those skilledin the art will recognize that the embodiments will usually be used withand can readily be adapted to multiple-cylinder engines with multiplevalves per cylinder.

While the present system employs elements which are well known to thoseskilled in the art of internal combustion engine design, it combinesthese elements in a novel way which produces one or more new results notheretofore discovered. Accordingly the scope of this invention should bedetermined, not by the embodiments illustrated, but by the appendedclaims and their legal equivalents.

1. An internal combustion engine having a rotatable camshaft, at leastone cylinder having at least one valve coupled to said camshaft andarranged to open and close a port in said cylinder, an improvementcomprising coupling means for coupling said valve to said camshaft suchthat rotation of said camshaft alternately (a) cams said valve to anopen position that opens said port, and (b) cams said valve to an closedposition that closes said port, whereby strong valve springs do not haveto be compressed during engine operation, resulting in improved engineefficiency through reduced fuel consumption, a lighter engine, lowerengine wear, less heat, and improved engine performance.
 2. The internalcombustion engine of claim 1 wherein said coupling means comprises atleast one rocker arm that follows said camshaft and seesaws in responseto rotation of said camshaft and thereby forces said valve between saidopen and closed positions in response to the seesaw movement of saidrocker arm.
 3. The internal combustion engine of claim 2 wherein saidcoupling means also comprises a rod that reciprocates with said seesawmovement of said rocker arm and couples said rocker arm to said valve,said valve having a stem that has a pair of facing shoulders thatsandwich said rod, one of said rod and said stem having a holetherethrough, the other of said rod and said stem extending through saidhole.
 4. A rocker arm assembly for opening and closing a valve having astem in a reciprocating, internal combustion engine, comprising: acamshaft arranged to rotate with said engine and having first and secondattached cams, a rocker arm mounted on a pivot and having a pair of camfollowers, namely a tip and a seat, said tip of said rocker arm beingarranged to follow said first cam, and said seat of said rocker armbeing arranged to follow said second cam so that said rocker arm willrock back and forth in a seesaw movement when said engine runs, a rodattached to said rocker arm and arranged to reciprocate in response tosaid seesaw movement of said rocker arm, said stem of said valve beingattached to said rod so that as said camshaft rotates, said second camfirst urges said seat of said rocker arm and said rocker arm to move ina first direction, thereby causing said rod to open said valve, thensaid first cam urges said tip of said rocker arm and said rocker arm tomove in the opposite direction, thereby closing said rod to close saidvalve whereby strong valve springs do not have to be compressed duringengine operation, resulting in improved engine efficiency throughreduced fuel consumption, a lighter engine, lower engine wear, lessheat, and improved engine performance.
 5. The assembly of claim 4,further including a spring interposed between the end of said stem andsaid pin.
 6. The assembly of claim 4, further including a fasteneraffixed to said stem for retaining said spring.
 7. The assembly of claim6 wherein said fastener is selected from the group consisting ofadjustable and non-adjustable fasteners.
 8. The assembly of claim 4wherein said stem of said valve has a pair of facing shoulders that aremoved in respectively opposite directions by said rod.
 9. A rocker armassembly for opening and closing a valve with a stem in a reciprocating,internal combustion engine, comprising: a rocker arm mounted on a pivotand arranged to rock back and forth in a seesaw movement, said rockerarm having a pair of cam followers, namely a tip and a seat, a pin beingattached to said rocker arm and arranged to reciprocate in response tosaid seesaw movement of said rocker arm, said stem of said valve beingattached to said pin, said arm being arranged to rotate about saidpivot, said tip being arranged to follow a first cam, said seat beingarranged to follow a second cam, said first cam being attached to afirst camshaft, said second cam being attached to a second camshaft,said first and said second camshafts being arranged to rotatesynchronously with the crankshaft of said engine, so that as said secondcamshaft rotates, said second cam urges said seat and said arm to movein a first direction, thereby opening said valve, and as said firstcamshaft rotates, said first cam urges said tip and said arm to move inthe opposite direction, thereby rotating said arm in a second directionand closing said valve, whereby strong valve springs do not have to becompressed during engine operation, resulting in improved engineefficiency through reduced fuel consumption, a lighter engine, lowerengine wear, less heat, and improved engine performance.
 10. Theassembly of claim 9, further including a spring interposed between theend of said stem and said pin.
 11. The assembly of claim 9, furtherincluding a fastener affixed to said stem for retaining said spring. 12.The assembly of claim 11 wherein said fastener is selected from thegroup consisting of adjustable and non-adjustable fasteners.
 13. Theassembly of claim 9 wherein said stem of said valve has a pair of facingshoulders that are moved in respectively opposite directions by saidrod.
 14. A method for opening a valve in a reciprocating, internalcombustion engine, comprising: providing a valve with a stem, said valvebeing arranged to close a port in a cylinder when said valve is in aclosed position and open said port when said valve is in a closedposition, providing a rocker arm having two cam followers, namely, a tipand a seat, said rocker arm mounted on a first shaft and being arrangedto pivot on said first shaft, providing a first cam having a first lobeand arranged to rotate in response to operation of said engine,providing a second cam having a second lobe and arranged to rotate inresponse to operation of said engine, said tip and said seat of saidrocker arm being arranged to follow said first and second lobes of saidfirst and second cams so that said rocker arm reciprocates in responseto rotation of said engine, providing a rod, said rod being attached tosaid stem of said valve and said rocker arm and arranged to cause saidvalve to open and close in response to reciprocation of said rocker arm,so that when said tip is urged by said first cam, said valve is urgedinto a closed position, and when said seat is urged by said second cam,said valve is urged into an open position, whereby strong valve springsdo not have to be compressed during engine operation, resulting inimproved engine efficiency through reduced fuel consumption, a lighterengine, lower engine wear, less heat, and improved engine performance.15. The method of claim 14, further including a spring interposedbetween an end of said stem and said pin.
 16. The method of claim 14,further including a fastener affixed to said stem for retaining saidspring.
 17. The method of claim 16 wherein said fastener is selectedfrom the group consisting of adjustable and non-adjustable fasteners.18. The method of claim 14 wherein said stem of said valve has a pair offacing shoulders that are moved in respectively opposite directions bysaid rod.
 19. The method of claim 14 wherein said first and second camsare mounted on a common camshaft.
 20. The method of claim 14 whereinsaid first and second cams are mounted on first and second camshafts,respectively.
 21. The method of claim 14 wherein said stem of said valveextends through a hole in said rod.
 22. The method of claim 14 whereinone of said first and second lobes of said first and second cams isrelatively long and the other of said lobes is relatively short.